CRCST Sterilization Methods 2 — Questions and Answers
Question 1: What is the primary mechanism by which ethylene oxide (EtO) achieves sterilization?
- Oxidizing cell membranes
- Alkylating DNA and proteins (Correct answer)
- Denaturing enzymes with heat
- Disrupting cell wall synthesis
Correct answer: Alkylating DNA and proteins
EtO sterilizes by alkylating the DNA and proteins of microorganisms, preventing reproduction and causing cell death.
Question 2: Which parameter is NOT part of the EtO sterilization cycle?
- Gas concentration
- Relative humidity
- UV exposure (Correct answer)
- Temperature
Correct answer: UV exposure
UV exposure is not a parameter in EtO sterilization; the key parameters are gas concentration, humidity, temperature, and exposure time.
Question 3: Hydrogen peroxide gas plasma sterilization is contraindicated for items made of which material?
- Stainless steel
- Cellulose-based materials (Correct answer)
- Polypropylene
- Titanium
Correct answer: Cellulose-based materials
Cellulose-based materials (paper, linen, cotton) absorb hydrogen peroxide and are incompatible with H2O2 gas plasma sterilization.
Question 4: What does the term 'D-value' represent in sterilization science?
- The dose of sterilant required to kill all spores
- The time needed to reduce a microbial population by 90% (Correct answer)
- The depth of penetration of steam into a pack
- The dwell time at peak sterilization temperature
Correct answer: The time needed to reduce a microbial population by 90%
The D-value (decimal reduction time) is the time required to reduce a microbial population by one log (90%) at a given set of conditions.
Question 5: Which biological indicator organism is the standard for validating steam sterilization cycles?
- Bacillus atrophaeus
- Geobacillus stearothermophilus (Correct answer)
- Clostridium sporogenes
- Bacillus cereus
Correct answer: Geobacillus stearothermophilus
Geobacillus stearothermophilus spores are the standard biological indicator for steam sterilization because of their high heat resistance.
Question 6: When using dry heat sterilization at 160°C, what is the standard minimum exposure time?
- 30 minutes
- 60 minutes
- 120 minutes (Correct answer)
- 180 minutes
Correct answer: 120 minutes
Dry heat sterilization at 160°C requires a minimum exposure time of 120 minutes to achieve sterilization.
Question 7: Which sterilization method is most appropriate for prion-contaminated instruments?
- EtO gas sterilization
- Hydrogen peroxide gas plasma
- Extended gravity steam at 134°C for 18 minutes (Correct answer)
- Dry heat at 121°C
Correct answer: Extended gravity steam at 134°C for 18 minutes
Prions are highly resistant; extended prevacuum steam cycles at 134°C for a minimum of 18 minutes are recommended by the WHO for prion decontamination.
CRCST Sterilization Methods 2
What is the primary mechanism by which ethylene oxide (EtO) achieves sterilization?